1. Field of the Invention
The present invention relates to a servo valve for power steering boosters.
2. Description of the Prior Art
In incorporating a hydraulic power steering mechanism into a steering system of a vehicle, particularly an automobile, it is desired for the steering mechanism to be as small as possible because the space to be occupied thereby is generally limited. On the other hand, in order to obtain a proper steering feeling for an operator, it is required to apply hydraulic pressure and/or spring reaction to the steering system. For this purpose, in the prior art, springs have been located at ends of a spool of a servo valve for such kinds of the boosters against the axial displacement of the spool. With this arrangement, there has been a tendency of the servo valve to be unduly elongated.
With another servo valve hitherto used, a spool of the valve is formed hollow within which are located a pair of reaction pistons and a single spring. However, it has been difficult, if not impossible, for reaction supporting parts of this valve to be machined with a desired dimensional accuracy in their length.